The present invention relates to multi-rotor screw compressors and, more particularly, to improved porting configurations for same.
Twin screw compressors are known, and typically relate to a compressor having a housing defining rotating chambers for two rotors, and such compressors typically have a number of various ports. The primary ports are suction and discharge ports, and additional ports which are typically utilized in screw compressors include a first closed lobe (FCL) port, a last closed lobe (LCL) port, economizer ports and other pressure-balancing ports. Each of these ports performs a different system function in connection with compressor operation.
Multi-rotor screw compressors are known and have housings defining more than two rotor chambers, with three or more rotors defining at least two parallel pairs, each of which can act as an independent compressor pair. Providing the various ports as outlined above for such a compressor can cause difficulty because, depending upon compressor design details and system operating conditions, the various ports can interact with each other. This interaction can substantially interfere with efficient operation of the compressor.
Based upon the foregoing, it is clear that the need remains for improved housing and porting structures for multi-rotor screw compressors.
It is therefore the primary object of the present invention to provide improved housing and porting structures for such compressors, whereby the compressor can operate more efficiently.
It is a further object of the present invention to provide such porting for a multi-rotor screw compressor which reduces noise of operation as well.
Other objects and advantages of the present invention will appear hereinbelow.
In accordance with the present invention, the foregoing objects and advantages have been readily attained.
According the invention, a multi-rotor screw compressor is provided, which comprises a compressor housing defining at least three parallel rotor housing sections, each rotor housing section containing a rotor, and adjacent rotors defining at least two compressor pairs, said housing further including a suction port and a discharge port for each of said compressor pairs, and further comprising at least two additional ports selected from the group consisting of first closed lobe ports, last closed lobe ports, and economizer ports, wherein at least one of said additional ports is communicated with a first pair of said at least two pairs, and another of said additional ports is communicated with a second pair of said at least two pairs whereby interaction between said additional ports is reduced.
In further accordance with the present invention, only a single pair of the multiple pairs of the screw compressor is provided with an economizer port, and the discharge ports for the multiple pairs are selectively sized so as to provide the economized pair with a lower volume index ratio than the non-economized pair. This helps provide for efficient compressor operation and also reduces noise due to pressure pulsation and the like.
Asymmetrical distribution of ports in accordance with the present invention can advantageously be utilized to provide for efficient operation of the multi-rotor screw compressor, while also avoiding interaction between ports so as to improve overall performance of same.